Thread: Discussion spark ignition diesel...
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Old Nov 22, 2012, 06:56 AM
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Don't get me wrong... If you think that you can get it to work... then go for it, and let us know what happens. Also... I totally agree. $4/gal sux. But, get a car/engine that is designed to burn it.

I've been tuning engines for a long time (see the screen name)... and I've played with dang near every fuel that can be used. Along with that... I own a custom bike shop, and I like diesel. (Oh... and I have a degree in experimental Physics)

I can help with any info you may want, to help you with your experiment.

The problem with using oil for a fuel (Any form of diesel) is that it burns slow, and is hard to ignite. So... way back when... rudolf diesel decided to make an engine that would simply raise the temps, internal of the engine to the oil's auto-ignite temp. In doing that... he also was compressing the fuel to a point that would accelerate the burn.

Above, you say "A Cummins is different than a spark ignition engine." And you are absolutely right. As I already said... the main difference is in the cyl pressures before ignition. With the relatively low cyl pressure of a typical spark ignition engine.. you won't be able to extract enough energy out of the fuel before the end of the "Power" cycle. You make mention of "Complete combustion"... but an engine turning 3000 RPM only has a fraction of a second to make that combustion happen. (With out exploding the fuel)

With that said... how do plan on getting complete combustion inside an engine with low cyl pressure, and volumetrically designed to spin as high 6000 RPM? (FYI... my Cummins has a redline of 3200 rpm, and makes peak torque at 1900)

As a final FYI... Back in the late 70's, early 80's... Chevy tried to do a similar experiment. They basically took their 350 gas engine, and put high compression heads on it... with dished pistons... and tried to sell it as a diesel. It was a piss-poor engine, and it didn't live long. Also, it was HIGHLY inefficient. Most of the world is split 50/50 gas/diesel... but in the USA... we are mostly gas in the consumer market. And that's mostly becasue of the F-ups that the "Big 4" did in the 70's... and that kept the market from growing. And... to this day... they keep saying... "The American Market doesn't want diesel !!!" Personally... that's a bunch of bull !!! If the car companies would bring in some good diesels, and give the same incentives as gas... people would buy them. (The MPG alone would sell them) Since you are looking at Diesel... here's some things to think about.

1) VW's "Sign and drive event" that is currently going on... EXCLUDES the TDi cars.

2) Toyota has been selling diesel versions since the 60's. They won't bring them into the USA because of our "dirty fuel." Well, we now burn ULSD, and they still won't bring them into the country.

3) Ford, Dodge, and Chevy all had a 1/2 ton diesel truck ready to come out... and then they never were released because "of the bad economy." Cummins designed a brand new V8 5ltr engine for the Ram 1500, and the project was scrapped.

4) The only government subsidies for Bio-Diesel is to produce fuel from Soy. Soy beans have almost NO oil in them, and the extraction process uses caustic chemicals. You can get more oil out of old (used) coffee grounds. (and that's reusing waste, not a farm product)

As I said before... I like diesel.
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Last edited by Dr Honda; Nov 22, 2012 at 07:10 AM.
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